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Stephen, the ripple sizes in your pictures are only a fraction of what I see in my working 106. Perhaps they are so small because the 4 tubes never conduct.
Even with almost exhausted tubes you should get some output square wave.
I would measure the waveform at the grid line w.r.t. the DC cathode voltage(s). And then consult Ia-Vg characteristics of the EL84.
Albert

Greetings
I sent you an email offlist as I may have some resources willing to help ID this. Let me know if you want me to ask them for help.
-ls-

Hello--

I'm offering FS one only? Tektronix 02-1004-402 (s/n 27694) power supply for the 4957;

it's untested but in VG cosmetic condition.

graphics tablet. The power supply sources +12 VDC @ 0.3 A and -12 VDC? @0.1 A.

I'm asking $7.50 plus USPS postage.

Questions welcomed, PayPal honored.

Thanks, and 73--

Brad? AA1IP

On Tue, Mar 1, 2022 at 10:04 PM, Dave Wise wrote:

Stephen, I mentioned the socket mod as a PSA. I wasn’t exhorting you to do
it.

I get it. Sorry if I misunderstood you.

Stephen, I mentioned the socket mod as a PSA. I wasn’t exhorting you to do it.

From: [email protected] <[email protected]> On Behalf Of Stephen via groups.io
Sent: Tuesday, March 01, 2022 1:02 PM
To: [email protected]
Subject: Re: [TekScopes] Type 106 Saga (Again)

I’ve rechecked all the tubes, and they still read very strong on my HealthKit tester. Since a I had a quad of EL84’s laying around, I replaced all of them as precaution. They’re not brand new, but they read very strong as well. That didn’t make any change.
The DTPT switch seems to be ok. Although I can’t seem to locate the B side on the schematic.
I haven’t checked R55 yet.

David, are you suggesting that I rewire the tube sockets, even though everything was working properly before with EL84’s?

I’ve rechecked all the tubes, and they still read very strong on my HealthKit tester. Since a I had a quad of EL84’s laying around, I replaced all of them as precaution. They’re not brand new, but they read very strong as well. That didn’t make any change.
The DTPT switch seems to be ok. Although I can’t seem to locate the B side on the schematic.
I haven’t checked R55 yet.

David, are you suggesting that I rewire the tube sockets, even though everything was working properly before with EL84’s?

On Tue, Mar 1, 2022 at 10:29 AM, Colin Herbert wrote:

A2Q9 base-emitter junction shows infinite resistance one way and
452K the other.

Ideally if you have "diode check" mode on your DVM that is what you need to use with the transistor off but all indications point to a faulty A2Q9.

Both A2Q8 and A2Q9 were Motorola SM4713 originally and it looks as though a
2N3251 would be an equivalent now, though they are ?2.40 each.

For now you can use widely available 2N3906 to get your debug going. I don't have this equipment and didn't look at the design carefully so there may be better equivalents recommended by group members.

Ozan

To work with 6BQ5/7189, a minor wiring change is needed. Pins 1 and 6 are “unspecified internal connection” while the corresponding 7189A pins are explicitly G1 and G2 respectively.
On all four sockets, move the G2 wire from pin 6 to pin 9. That is all.
EL84 pins 1 and 6 are no-connect so this tube doesn’t need the mod.

The output tubes yank their plates toward their cathodes (which are being held at a negative voltage determined by the AMPLITUDE control), then release them and the load resistance pulls the line back up to ground.

As the tubes wear out, two things happen. (1) Cathode emission decreases. This ultimately limits the maximum negative excursion. (2) Sometimes the cathode develops an “interface layer” which acts like an RC time constant. Since only the positive corner’s quality is specified in HI AMPLITUDE mode, this doesn’t matter unless it becomes so bad that it compromises the negative output in FAST RISE mode.

Dave Wise

From: [email protected] <[email protected]> On Behalf Of Stephen via groups.io
Sent: Tuesday, March 01, 2022 10:20 AM
To: [email protected]
Subject: Re: [TekScopes] Type 106 Saga (Again)

On Tue, Mar 1, 2022 at 06:39 PM, Dave Wise wrote:

In Fast Rise mode, the output tubes provide base drive to the Fast Rise
circuit. See SW242A on the schematic.
SW242B bypasses the AMPLITUDE control in Fast Rise mode, jamming it to
maximum. So don’t leave it running for hours in Fast Rise mode unless you
have lots of spare 7189A’s.

Dave Wise

Hmmm. I have left it on a few times for quite a long time…
Mine doesn’t have 7189A’s. It has old Philips EL84’s which read very strong. But I’ll check them again when I get back.

I’ll report back when I can get check all that tou guys suggested.

And thanks for the tip regarding preserving the tube life. I’ll certainly be more careful now….

I was thinking about the 475A, but I really don't need it.
-Dave

Hi Ozan,
I checked both A2Q8 and A2Q9 with my checker and they both gave B of about 78 and uG at 752. I'm guessing that these show the transistors to be OK, but I am definitely rusty on this stuff - I might be getting everything wrong. I admit to giving A2Q9 a bit of a "cooking" when I put it back into circuit, but I don't think I ruined it.

Doing what you suggested to A2Q9, the base looks to be connected to ground OK with the device off and checking the resistance to ground; the voltage with the device turned on gives zero volts (I may have been making this measure incorrectly before, because the space available was small). With the power turned off, A2Q9 base-emitter junction shows infinite resistance one way and 452K the other.

Both A2Q8 and A2Q9 were Motorola SM4713 originally and it looks as though a 2N3251 would be an equivalent now, though they are ?2.40 each.
Colin.

On Tue, Mar 1, 2022 at 06:39 PM, Dave Wise wrote:

In Fast Rise mode, the output tubes provide base drive to the Fast Rise
circuit. See SW242A on the schematic.
SW242B bypasses the AMPLITUDE control in Fast Rise mode, jamming it to
maximum. So don’t leave it running for hours in Fast Rise mode unless you
have lots of spare 7189A’s.

Dave Wise

Hmmm. I have left it on a few times for quite a long time…
Mine doesn’t have 7189A’s. It has old Philips EL84’s which read very strong. But I’ll check them again when I get back.

I’ll report back when I can get check all that tou guys suggested.

And thanks for the tip regarding preserving the tube life. I’ll certainly be more careful now….

In Fast Rise mode, the output tubes provide base drive to the Fast Rise circuit. See SW242A on the schematic.
SW242B bypasses the AMPLITUDE control in Fast Rise mode, jamming it to maximum. So don’t leave it running for hours in Fast Rise mode unless you have lots of spare 7189A’s.

Dave Wise

From: [email protected] <[email protected]> On Behalf Of Stephen via groups.io
Sent: Tuesday, March 01, 2022 9:15 AM
To: [email protected]
Subject: Re: [TekScopes] Type 106 Saga (Again)

On Tue, Mar 1, 2022 at 05:55 PM, Albert Otten wrote:

Interleaved.

Broken switch SW242A? In High Ampl mode you should measure R99 600R at the GR
output plug.
What would happen when R55 is open?
Is the output 0V or some constant negative voltage?

Thanks Albert,

Interesting…. I didn’t think of a broken switch. I check that out when I’ll get beck home later.
I’ll check again, but from memory all of the outputs are pretty close to 0V. I’ll check that again.

I’ll also check R55.

I don't think this is weird. The -20 V on top of "A" supplies the grid and
trigger circuits. The 4x output tubes anode currents flow in a separate
circuit from GND to "A", regulated by anode-cathode voltage, not by grid
amplitude.

Ok, but the 4 output tubes only supply the High Amplitude section, if I understood correctly.

Why would all outputs be out? That must be caused by something they all share in common.
Maybe the switch…

Albert

On Tue, Mar 1, 2022 at 05:55 PM, Albert Otten wrote:

Interleaved.

Broken switch SW242A? In High Ampl mode you should measure R99 600R at the GR
output plug.
What would happen when R55 is open?
Is the output 0V or some constant negative voltage?

Thanks Albert,

Interesting…. I didn’t think of a broken switch. I check that out when I’ll get beck home later.
I’ll check again, but from memory all of the outputs are pretty close to 0V. I’ll check that again.

I’ll also check R55.

I don't think this is weird. The -20 V on top of "A" supplies the grid and
trigger circuits. The 4x output tubes anode currents flow in a separate
circuit from GND to "A", regulated by anode-cathode voltage, not by grid
amplitude.

Ok, but the 4 output tubes only supply the High Amplitude section, if I understood correctly.

Why would all outputs be out? That must be caused by something they all share in common.
Maybe the switch…

Albert

On Mon, Feb 28, 2022 at 07:38 PM, Stephen wrote:

My type 106 was working fine until a few days ago when I had no more output at
all on any output. Neither the High Amplitude nor the +/- Fast Rise.

Broken switch SW242A? In High Ampl mode you should measure R99 600R at the GR output plug.
What would happen when R55 is open?
Is the output 0V or some constant negative voltage?

Now the last one (-20) is extremely weird as the square waves follow the frequency I set on the unit, but not the amplitude at all.

I don't think this is weird. The -20 V on top of "A" supplies the grid and trigger circuits. The 4x output tubes anode currents flow in a separate circuit from GND to "A", regulated by anode-cathode voltage, not by grid amplitude.

Albert

On Tue, Mar 1, 2022 at 07:34 AM, Colin Herbert wrote:

...
I removed the two transistors A2Q9 and A2Q8 and they
both check as OK with my MK-328 transistor-checker.
....
Puzzlingly, there
doesn't seem to be any current at all passing through A2R44 (100R) or
A2Q8.The voltage seems to be at 24.5 VDC from TP2 (should be +8 VDC) all the
way to the collector of A2Q8 (should be +0.77 VDC). The voltages at pins 10
and 11 of the A2 board are both about -24.7 VDC with respect to ground, not
the -4 VDC that they should be.

A2Q9 can't be good if its emitter (=collector of A2Q8) is sitting at 20+ volts. You should see one Vbe above ground since base is grounded. Unlikely but ground connection of the base could be bad too (i.e. base is not really connected to ground anymore).

If you check A2Q9 base-emitter junction do you see a diode? If you check connectivity between base of A2Q9 and ground when the unit is off do you see essentially zero ohms?

Ozan

Hi All,
I have looked on the "HP-Agilent-Keysight" group and either I am not getting
to the correct place (always possible), or I am missing something. I looked
at the Meter Amplifier (Board A2) and replaced three capacitors (C26, C27
and C28) all to no avail. The meter needle still initially swings well to
the right and eventually settles down on zero. The trouble is, that this
happens if the FUNCTION switch is in any of the positions (VOLTMETER, SET
LEVEL or DISTORTION). I removed the two transistors A2Q9 and A2Q8 and they
both check as OK with my MK-328 transistor-checker. Puzzlingly, there
doesn't seem to be any current at all passing through A2R44 (100R) or
A2Q8.The voltage seems to be at 24.5 VDC from TP2 (should be +8 VDC) all the
way to the collector of A2Q8 (should be +0.77 VDC). The voltages at pins 10
and 11 of the A2 board are both about -24.7 VDC with respect to ground, not
the -4 VDC that they should be. Pin 13 is correctly at 24.9 VDC and pin 5 at
-24.9 VDC as they should be. These are all at the correct voltages whether
the FUNCTION switch is on any of its positions (VOLTMETER, SET LEVEL or
DISTORTION). I have thought about other things and I am stumped for an
answer to this, does anyone have a credible answer, especially since the
apparatus seemed to be OK before it was stored for a while?
Thanks again, Colin.

On Fri, Feb 25, 2022 at 11:22 AM, NigelP wrote:

I'm looking for two 366-2041-00 knob caps (with the index bar). I only need
caps, not the inserts.

The plastic caps are known to become brittle with time, making their inside "wings" break. That's one of the main causes why these knobs are missing so often. It's a good idea to carefully preheat the caps to soften them, before clipping them on.

Raymond

I'm in the UK.....

regards

Nigel

Hi Christophe,

Congrats on the repair, I'm glad I could help.

Szabolcs


clunche via groups.io <clunche@...> ezt írta (id?pont:
2022. febr. 28., H, 20:56):

Hello Nigel,

I have two for you if you have not found them yet closer. Where are you located? I'm in the Netherlands.

Jaap